Incandescent electric lamp



n 6, 1938. A. N. CLAUDE 2,115,480

INCANDESCENT ELECTRIC LAMP Filed Jan. 17, 1935 I INVC/YTOR ANDRE NICOLAS CLA UDE B [M 72%, 5M? 0kg HTTOQNLVS Patented Apr. 26, 1938 k 2,1

UNITED", STATES PATENT orrica' mcmasoan'r amc'rarc LAMP Andre Nicolas Claude, Nanterrc, France, assignor to Socit Anonyme pour-lea Applications dc -i'Electricit et des Gas Bares Etablissements f Claude-Pu & Silva, a corporation of France Application January 17, 1935, Serial No. 2,268

In France January as, 1934 8 Claims. (Cl. 17616) The present invention relates to incandescent electric lamps, the atmosphere of which contains krypton and xenon. The use of each of these gases in such lamps has already been indicated by Mr. Georges Claude on several occasions, for example in a lecture given on the 22nd March, 1918 to the Socit des Ingenieurs Civils.

Applicant has studied the use of diil'erent mixtures of k ypton and xenon and has found that, contrary to what could be expected, the increase in the efiiciency and the diminution in the diffusion of the vapour of tungsten, which generally constitutes the filament, which are due to the presence of xenon, are much more considerable for a small proportion of xenon, for instance from 5 to than if they varied linearly as a function of the xenon content.

Thus, for lamps which are identical in regard to filaments and bulbs, but which differ in regard to gaseous atmospheres, it has been found that, for one and the same life, the efficiencies of three lamps filled respectively (1) with pure krypton, (2) with a mixture of 90% of krypton and 10% of xenon, (3) with pure xenon, exceed respectively by 30, 40, and 50% the efficiency of a lamp filled in the usual manner with argon having a notable proportion of nitrogen.

Thus, it has been found that, as compared to a lamp filled in the usual manner with argon with a notable content in nitrogen, the same lamp containing pure krypton has its light efiiciency increased by 30%, and by 50% when containing pure xenon, whereas half of this gain from 30% to 50% is already achieved by adding to the krypton only 10% of the expensive xenon, tR addition of the remaining 90% xenon achieving only a further 10% gain in efllciency. The present invention therefore consists in the industrial utilization of this discovery by filling the lamps with akrypton-xenon mixture having a xenon content between 5 and 20%, whereby with such a very moderate percentage of the more expensive xenon a surprising and more than proportionate gain in efficiency is achieved. However, to 5 achieve the best results with a mixture of krypton and xenon, certain precautions should be observed.

In the first place, it is necessary to avoid the production of arcs between the current leads 50 while the lamp is running.

By proceeding in the manner known and employed for twenty years for argon, that is to say, by adding a considerable proportion of nitrogen, 2. very considerable loss in efilciency results. 55 Nitrogen may in fact be added without considerable inconvenience to argon, the thermal conductivity and molecular weight of argon and nitrogen being rather close, but it is not the case with heavy and poor-conducting gases such as krypton and xenon. 5

Furthermore, at the particularly high working temperature of these lamps, nitrogen in an excessive quantity very rapidly attacks the filament.

The quantity of nitrogen which may be added ought therefore to remain small. 10

Experience has shown that it is then not always possible, particularly if the volume of the lamp is small, to avoid the formation oi arcs between the current leads constituted, as is generally the case, by nickel. 15

Applicant has found that the starting of arcs was due to the electronic emission of the nickel, the temperature of which is rather high in the vicinity of the filament. In krypton and xenon lamps, therefore, nickel current leads or con- 50 ducting wires will be replaced by leads or conducting wires made of a metal of small emissive power such as molybdenum, or an alloy of small emissive power such as ferro-nickel, or even a metal which may be emissive but which has a 35 coating of small emissive power.

This replacement is particularly advantageous with coiled filament incandescent lamps in which the temperature of the filament is higher and the tendency to the formation of arcs is more pro- 30 nounced.

On the other hand, the arrangement of the winding of the filament in existing lamps has the disadvantage of diminishing the luminous efficiency, due it appears to the reflection which the 5 rays of light emitted by certain parts of the filament have to undergo before reaching the walls of the lamp. This part of the emciency, however, is proportionally more considerable in lamps filled according to the present invention with the 40 krypton-xenon mixture, which is a very bad conductor of heat.

In order to reduce the proportion of reflected rays, there will then be employed a filament coiled in a helix the turns of which will be more spaced than those of the filaments employed at present. The additional loss of heat resulting therefrom will be less than the gain in light.

In all cases, a useful precaution will consist in placing in the known manner one or more fuses in the lamp base to avoid the persistence of the arcs which may be formed in the event that the filament of the lamp breaks.

In the single figure of the drawing which is a diagrammatic side, elevational view, there is illustrated by way of example a lamp embodying the features of the invention.

The lamp oi the present invention comprises a tube V filled with a mixture oi krypton and xenon with xenon in the proportion of between 5 and 20%. The incandescent electrode 1' consists of a filament of tungsten wound in helical form and provided with lead wires for conveying the current to the filament. The lead wires A are made or term-nickel and fuses f are provided in the base oi the lamp.

I claim:

1. An incandescent electric lamp having an atmosphere consisting substantially oi krypton and xenon, the proportion oi xenon in the krypton-xenon mixture ranging between 5 and 20%.

2. An incandescent electric lamp as claimed in claim 1, including an incandescent filament and non-emisslve leads for supplying current to the incandescent filament within the gaseous space.

3. An incandescent electric lamp as claimed in claim 1 including a filament wound in a helix of relatively large pitch.

4. An incandescent electric lamp as claimed in claim 1 including a filament, and molybdenum leads within the gaseous space for conducting current to the filament.

5. An incandescent electric lamp as claimed in claim 1 including a filament, and leads within the gaseous space coated with -a non-emissive substance for conducting current to the filament.

6. An incandescent electric lamp having an atmosphere consisting substantially of krypton and xenon with a proportion of xenon between 5 and 20%, a filament in the form of a simple helix oi relatively large pitch, and non-emissive wires within the gaseous space for conveying current to the filament.

7. An incandescent electric lamp having a gaseous filling consisting substantially of a mixture oi krypton and xenon, the proportion of xenon in the mixture lying between 5 and 20%, a tungsten filament, and non-arcing ferro-nickel leads connected to said filament.

8. An incandescent electric lamp as claimed in claim 1, in which the atmosphere contains a small quantity of nitrogen in addition to the krypton and xenon.

ANDRE NICOLAS CLAUDE. 

